Electromagnetic switches



Nov. 3, 1959 A. D. PRICKETT ELECTROMAGNETIC SWITCHES Filed June 16, 1958 lllll llln 1121 612:2501 A P L CA' 6-251;

United States Patent ELECTROMAGNETIC SWITCHES Alfred Donald Prickett, Handsworth Wood, Birmingham, England, assignor to Joseph Lucas (Industries) Limited, Birmingham, England Application June 16, 1958, Serial No. 742,173

Claims priority, application Great Britain June 26, 1957 1 Claim. (Cl. 200-95) This invention relates to electromagnetic switches such as are used in dynamo voltage or current regulators, automatic cut-outs for interconnecting a dynamo and battery or for other like purposes and of the kind comprising an electromagnet, an armature for actuating a movable contact piece, and a blade spring for loading the armature in opposition to the electromagnet.

The object of the invention is to provide a convenient means for adjusting the force exerted by the spring on the armature, and particularly a means for enabling the adjustment of the spring in the course of bulk production of switches for a given duty to be effected expeditiously.

A spring adjusting means in accordance with the invention comprises a cam rotatably mounted on the switch frame in contact with the free end of the spring, and having a segmental toothed rack formed thereon for actuation by a complementary toothed tool.

In the accompanying drawings:

Figure 1 is a side view, Figure 2 isa plan, and Figure 3 an end view of a dynamo voltage regulator embodying the invention.

Referring to the drawings, the construction there shown comprises a frame a made from an iron bar bent to form a base and two vertical side members at the ends of the base. On the base is secured a vertical iron core b which carries the exciting winding 0. The armature d for carrying or actuating a movable contact piece e is of L- shape, and one arm of it extends across the upper end of the said core. The armature is hingedly attached to the upper end of one of the side members of the frame by a spring blade 1. The spring for loading the armature may be an extension of the hinge blade, or it may consist of a separate blade g secured to the armature. In either case the loading spring extends over the upper end of the other side member of the frame.

The contact piece e co-operates with a complementary contact piece h carried by a spring blade i. The construction 'also includes the required circuit terminals,

Patented Nov. 3, 1959 but these are not shown as they are not necessary for elucidating the invention.

According to the invention there is attached to the outer face of the side member remote from the hinge an angularly movable adjuster. This consists of a sheet metal plate k and is attached to the said member by a pivot pin m. One part of the periphery of the plate is shaped to form a cam-like flange n for supporting the free end of the spring g. On an opposite part of the periphery of the plate is formed a segmental toothed rack 0. Adjacent to the rack there is formed in the side member a hole p for temporarily supporting one end of a tool provided with teeth for engaging the rack.

Adjustment of the force which the spring g exerts on the armature is effected by rotation of the adjuster by means of the said tool, the effect of the cam on the spring being to vary the flexure of the spring. After the adjustment has been made, the adjuster may be secured by a screw q inserted through a slot r in the adjuster into engagement with a hole in the side member of the frame.

The invention is applicable in essentially the same manner to cut-outs and other forms of electromagnetic switches of the kind above specified.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

An electromagnetic switch comprising in combination an electromagnet, a frame on which the electromagnet is mounted, an armature hingedly attached to the frame at one side, and extending over one end, of the electromagnet so as to be movable by the latter, a pair of complementary contact pieces one of which is movable by the armature, a blade spring attached to the armature and having a free end extending over the other side of the frame, a sheet metal plate pivoted to the last mentioned side of the frame and provided at opposite sides respectively of its pivot axis with a cam-like flange which serves to support the free end of the blade spring, and a segmental toothed rack which is engageable by a complementary toothed rotary tool for imparting angular adjusting movement to the plate, and thereby causing the cam-like flange to vary the flexure of the blade spring, the side of the frame to which the plate is pivoted being provided with a hole for temporarily supporting the tool while the latter engages the toothed rack.

References Cited in the file of this patent UNITED STATES PATENTS 241,213 Herrmann May 10, 1881 1,884,654 Gebhart Oct. 25, 1932 2,282,933 Cahill May 12, 1942' 2,693,553 Wells et a1. Nov. 2, 1954 

